This invention relates to adhesive compositions comprised of arylcyclobutene monomeric compositions.
Adhesive compositions are used in many industries to bond substrates together. Certain uses require that the adhesives employed therein possess certain high performance characteristics. For example, the aviation and aerospace industry requires that the adhesives possess bonding characteristics at temperatures much greater than 200.degree. C. Similarly, the electronics industry also requires such temperature performance as well as low thermal expansion, water resistance and low shrinkage upon bonding. Particularly, useful adhesives in the electronics industry are die attach materials. Such materials permanently bond the silicone chips to the semi-conductor package. In the finished device, the die attach provides a conductive path to remove heat from the chip and to provide an electrical ground.
Recently, polymeric materials have been employed as adhesives. Popular polymeric adhesives are conductive epoxies, urethanes, conductive polyimides, and acrylic polymers. Conductive epoxies are low viscosity pastes containing about 70 percent silver. Other metals, for example copper, and nickel, can be employed to reduce material costs. Urethanes are chosen to bond plastics, rubbers and fabrics because of their excellent elastomeric properties such as abrasion, tear and shock resistance. Urethanes lose their bonding strength above about 100.degree. C., so their use in applications where greater temperatures are encountered is not desirable.
Conductive polyimides comprise approximately 70 percent silver powder and a polyimide resin dissolved in an amide solvent. Some of the most popular polyimides are condensation polyimides from the reaction between benzophenonetetracarboxylic acid dianhydride and diamino benzophenone, and addition polyimides from ethanol and norbornene end-capped polyimides. A disadvantage associated with using polyimides is that their preparation produces volatile by-products and they contain organic solvents that are difficult to remove. If such organics vaporize or outgas they can cause degradation, as well as leaving voids in the final bond. A major problem of the polymeric adhesives is that they are brittle. The epoxies give low peel strength and exhibit poor thermal shock resistance. Another disadvantage of the known polymeric adhesives is that they fail at higher temperatures.
In view of the disadvantages of known methods, it would be desirable to provide an adhesive composition which can be employed to bond a variety of different solid substrates, wherein the bonding process does not produce the evolution of volatile gases. Moreover, an adhesive which can substantially retain its bonding properties at higher temperatures is also desirable.